1. Field of the Invention
The present invention relates to a wireless access system, and more particularly, to a method and apparatus for allocating a hybrid automatic repeat request (HARQ) channel identifier (ACID).
2. Related Art
Persistent allocation (PA) is one of scheduling methods for effectively allocating resources with respect to a connection having a periodic traffic pattern and a relatively fixed payload size.
When a base station (BS) periodically allocates a resource to a user equipment (UE) having a corresponding connection at a later time except for initial allocation, the BS allocates the resource without a control signal (e.g., A-MAP). When the resource is initially allocated through persistent allocation, the UE determines that the resource is periodically allocated through initially received resource allocation information, and exchanges traffic with respect to the BS by using an allocated resource area.
At present, resources are allocated based on the UE in the 802.16m system and persistent allocation is also achieved based on not a current service flow but the UE. Therefore, the UE cannot know for which flow (or connection) the area is allocated.
Therefore, if the UE has traffic for two or more connections at a time when a resource of uplink persistent allocation is allocated without a MAP, the UE transmits the traffic by the use of an uplink (UL) scheduler designated for a corresponding area. Herein, a case may occur in which traffic for a service flow for the persistent allocation is not transmitted.
To solve this problem, in a dynamic service addition (DSA) procedure in which a specific service is generated, if the service uses persistent allocation or the service is real-time traffic to which latency is important such as a voice over internet protocol (VoIP), several HARQ channel IDs (ACIDs) are pre-allocated to the service. The pre-allocated ACID is reserved for the service until the service is deleted (i.e., dynamic service deletion (DSD) procedure). If a resource for the allocated ACID is allocated, the UE transmits a packet for a service linked to the ACID through the allocated resource by assigning a top priority to the packet.
In this case, a resource linked to an ACID allocated to a specific service flow is restricted not to be used by another service flow until a corresponding service is deleted.